Extjs怎么在验证异常的时候就不提交了。

var fpanel =new Ext.form.FormPanel({         id:"ULFormPanel"+typeID,autoHeight: true,height:100,width:800,autoWidth: false,        frame: true,layout: "column",        items:[{columnWidth: .2, layout: "form",  items: [{ xtype: "textfield",width:120,id:"ULusernameens"+typeID,disabled:true,fieldLabel: "姓名(英)",vtype:"alpha",vtypeText:"请输入有效的英文名称"}]}]});var tbar=new Ext.Toolbar({        items:[  {id:'btnSaveUL'+typeID,text: '保存',style:{ "margin-left": "10px"},disabled:true,cls: 'x-btn-text-icon details',icon:"ExtJS/defaultImage/saveas.gif",                    handler: function() {//这个里面要如何判断啊？                   }}]});